Electrical transmission of communications



Patented Nov. 27, 1923.

PATENT OFFICE.

HAROLD ROWNTREE, 0F PASS CHRISTIAN, MISSISSIPPI.

ELECTRICALTRANSMISSION OF COMMUNICATIONS.

,N'o Drawing Application filed May 16,

Z '0 all whom it may concern:

Be it known that I, HAROLD Rowxrnrzn, a citizen of the United States, residing at Pass Christian, county of Harrison, State of Mississippi, have made a certain new and useful Invention in Electrical Transmission of Communications, of which the following is a specification.

This invention relates to the electrical transmission of intelligence such as is employed in wire or wireless telegraphy or telephony.

The object of the invention is to provide a system of communication which is simple in nature, efficient in operation and is especially designed to enable the secret communication by wire or wireless, whereby any particular receiving station or stat-ions would be the only ones who could intelligently receive the memages transmitted, although numerous other stations were equipped electri cally at least to receive such signals.

A further object of the invention is to utilize the principles herein involved and to provide a system which will enable the lifting of the limitation of transmitting stations to prevent interference therebetween when operating on the same or substantially the same characteristics of transmission.

Further objects of the invention will appear more fully hereinafter.

The invention consists in the method of transmission of intelligence, all as will be more fully hereinafter set forth and as pointed out in the appended claims.

\VhileI will now describe my invention as specifically applied to radio or wireless communication, I wish it to be understood that I do not desire to be limited or restricted thereto, as it will be apparent to those skilled in the art that the principles herein involved may equally well be applied to wire or wired wireless uses and subterranean signaling, such as is at present employed.

1 As is well known, the transmission of intelligence by wireless is accomplished by radiating electrical waves, and while the method of my invention may be utilized in connection with spark or damped wave signaling, as well as the various other types and forms of signal waves employed, for the sake of brevity I will confine the description of the method of my invention to continuous or undamped wave or are type of transmission, which will readily enable those skilled in the 1921. Serial No. 470,070.

art to understand the principles of my invention. 7

In the present state of the radio art, the growing ntunber of transmitting stations has necessitated the governmental control of the wave lengths of each transmitting station to prevent interference between the various radiated waves. The increasing number of amateur outfits, and commercial stations for that matter, is rendering the problem of interference effects more difficult and it will be readily seen that as time passes the maximum limit of wave length differentiation will have been reached. At the presout time, for example, the amateurs being confined within a strictly narrow zone of wave length, it will be but a short time when when it will be practically impossible for messages to be transmitted without intere ference with each other by the amateurs alone. Of course, as the commercial stations become more and more numerous, the same difficulty will be encountered in this respect.

Also at the present time the usefulness of the transmission of intelligence by wireless, especially for such purposes as war purposes, is seriously curtailed because intelligence carried by the radiated waves is available to all who possess an adequate receiving station. This has resulated in the adoption and use of complicated code systems, any and all of which are capable of being deciphered. Various attempts have been made to render the radiated signal wave secret by the use of special, complicated, expensive and more or less ineffectual arrangements of circuits at both the transmitting and receiving stations or either one of them, so that only one receiving station could detect the message conveyed by its related transmitting station., For various reasons such systems have proven entirely impracticable. lVhere the complicated transmitting circuit is employed, parasitic disturbances have prevented the efficient operation of the system. Furthermore, where extremely delicate receiving equipment is required, such systems have defeated their own ends, for in such instances when the detection of the secret signals is too difficult for others, it is apt to be too difficult for the station designed to receive the signals. The main difficulty, how ever, has been as above stated the great additional expense involved and the excessive decrease in efficiency due to the complication of circuits and the complication of operating conditions raised thereby.

It is among the special purposes of my in: vention to enable such radio or other type of message to be easily understandable at the receiving station or stations for which it IS intended, but to be wholly incapable of understanding, if not of detection, at any other receiving stations. and for each message to be unaffected by any other radio message no matter how many may be in operation at the same time. In other words, the system of my invention contemplates not only the adaptability of secrecy of sending and re ceiving but also the adaptability of decreasing the interference between transmitting stations to a negligible decree if not entirely. To accomplish this result, I employ a double modulation of the carrier wave. In other words, I doubly modulate the carrier Wave and this modulation I will refer to as being obtained (1) automatically, i. e., in a manner predetermined either mechanically or electrically effected, and (2) V011- tionally, i, e., by the signal to be transmitted. For example, applying the foregoing principle to continuous wave transmission, the automatic modulation of the carrier wave may be accomplished by varving the frequency thereof, the volitional modulation being accomplished for example by the signal such as the telegraph signal or in telephony the voice current.

Now it will be readily apparent that a.

double modulation effected in this manner, and provided the automatic modulation is of such a degree as to change rapidly and over a wide range. say for example the wave length of the radiated waves. which modulation is being etl'ected continuously in a predetermined sequence both as to type, characteristiand order, and the volitional modulation is simultaneously effected. will enable any receiving station which is tuned automatically or otherwise to receive the signals of the wave lengths of the transmitted signals in exactly the same so uence both as to time, characteristic, nature, type and order, as the transmitting station, to receive the message thus transmitted.

It will be apparent that if the'wave lengths employed at the transmitting station vary over a wide range, interference with other transmitting stations operating within that range is apt to'occur, but when the automatic modulation is varying rapidly, such possible interference can and will be but momentary, and would and could not in fact interefere with the reception of the signal due to the fact that with but mo Inentary stability of the signal wave, as distinguished from the interfering wave, when the transmitting and receiving stations employing my invention are maintained in symphonized resonance with each other, the

signal wave will be of constant characteris tie in the receiving phones, whereas the interfering waves will be of constantly varying characteristic, inaudible in one instance, faint the nextinstant, loud the next, inaudible the next, etc., so that no difliculty could be experienced by the receiving operator in continuously reading the signal being sent.

While I do not desire to be limited or re stricted to any particular means employed to effect the operation of the system of my invention, it will be apparent that my method may be utilized with the standard equipment and apparatus employed in the art at the present time. Whatever may be the type of automatic modulation of the car rier wave, which expression is employed in the sense of some variation of type, character or nature, of a predetermined sequential order, it will be understood that a corresponding variation of the electrical constants of the receiving station must be effected in synchronism with such modulation at the transmitting station, so as to insure the receiving station being in resonance or attuned to the transmitting station throughout such automatic modulation. In other words, as in the example above given, where a variation of wave length at the transmitting station is effected and the carrier wave volitionally modulated throughout such automatic modulation, then the receiving station requires constant tuning to enable the reception of the signals on the wave lengths employed atthe transmitting station by such automatic modulation of the carrier wave length. Such synchronism between transmitting and receiving stations may be accomplished in any manner, for example by a radiated wave such as is employed today in the wireless and wired wireless arts, for maintaining syuchronism between two stations.

From the foregoing it \\ill be seen that with the system of my invention not only is the limitation on the radio art lifted or at least enormously expanded, but a secrecy system of transmission is effected for commercial or governmental purposes, without necessitating code messages and without requiring complicated circuital arrangements, which of themselves will defeat the PHIJOSB of the system, because it is manifest that any receiving station that was not constantly being tuned into accord with the automatic modulations of the transmitting station would be unable to detect the volitional modulations.

It will be further seen that it provides a method of signaling which minimizes the possibility of interference between transmitted signals and prevents interference if and when occurring from rendering a message unreadable.

Many modifications and changes in details and adaptions of my method of transmission will readily occur to those skilled in the art without departing from the spirit and scope of my invention as above forth and as pointed out by the claims, and I, therefore, desire the foregoing description of the theory involved to be regarded in an illustrative sense and not in a limited sense.

Having now setset forth the objects and nature of my invention, however, and having shown its adaptability to one type of radio transmission, what I claim as new and useful, and of my own invention, and desire to secure by Letters Patent, is:

l. The method of electrical signaling which comprises continuously altering a plurality of characteristics of a transmitted carrier current in a predetermined sequence of nature, type or degree of alteration, and simultaneously modulating the carrier current in accordance with the signal to be transmitted.

2. The method of electrical signaling which comprises automatically altering a plurality of characteristics of a transmitted carrier current and "olitionally modulating said constantly altered carrier current in accordance with the signal to be transmitted.

3. The method of electrical signaling which comprises continuously altering a plurality of characteristics of a transmitted car rier current in a predetermined sequence of nature, type or degree of alteration, and simultaneously modulating the carrier current in accordance with the signal to be transmitted, and synchronously compensating for said carrier current alteration at the receiving station whereby said signal modu lation may be translated into signals.

4. The method of electrical signaling which comprises automatically altering a plurality of characteristics of av transmitted carrier current and volitionally modulating said constantly altered carrier current in accordance with the signal to be transmitted, and synchronously compensating for said carrier current alteration at the re station, and simultaneously modulating the transmitted carrier current in accordance with the signal to be transmitted.

6. The method of electrical signaling which consists of continuously altering a plurality of characteristics of a transmitted carrier current in a predetermined sequence of nature, type or degree of alteration, synchronously altering the related characteristics of the receiving station, and simultaneously modulating the transmitted current in accordance with the signal to be transmitted.

7. The method of electrical signaling which consists of continuously altering a plurality of characteristics of a transmitted carrier current and simultaneously altering the related characteristics of the receiving station, and simultaneously modulating the transmitted carrier current in accordance with the signal to be transmitted.

8. The method of electrical signaling which consists of continuously altering a plurality of characteristics of a transmitted carrier current in a predetermined sequence of nature, type or degree of alteration, simultaneously altering the related characteristics of the receiving station, and simultaneously modulating the transmitted currentin accordance with the signal to be transmitted.

I 9. The method of high frequency signaling which comprises continuously altering a plurality of characteristics of the radiated carrier wave in a predetermined sequence of nature, type or degree of alteration and simultaneously compensating the tuning at the receiving station for said carrier wave alterations, and modulating the continuously altering carrier wave in accordance with the signals to be transmitted.

10. The method of high frequency signaling which comprises continuously altering aplurality of characteristics of the radiated carrier wave in a predetermined sequence of nature, type or degree of alteration and synchronously compensating the tuning at the receiving station for said carrier wave alterations, and modulating the continuously altering carrier wave in accordance with the signals to be transmitted.

In testimony whereof I have hereunto set my hand on this 9" day of May, A. D. 1921. L

Y HAROLD ROWNTREE. 

